(1) Field of the Invention
The invention relates to a method for making a functional dental element and to a dental element obtainable by such method.
(2) Description of Related Art
Dental elements, such as crowns, are used in clinical practice mainly for replacing or correcting dental structures. This can involve partly or wholly lost teeth or molars. To date, materials for such elements have been examined in particular for technological/physical and chemical properties. Currently, in addition, the biological aspect plays an increasing role.
Dental elements can be fabricated from different materials. Examples include polymers, metals, composites, combinations of porcelain and metal, porcelain and other ceramic materials. Glass and ceramic materials form an ideal group of materials for dental elements, because they are hard, have a high wear resistance, are chemically inert in many media (biocompatibility), and can be simply formed into an aesthetic dental element. A broad application of these materials, however, is impeded by the inherent brittleness which is often the result of limitations in the fabricating process and of the material choice. Recent developments have led to different ceramic systems, such as sintered ceramic, glass-infiltrated ceramic and glass-ceramic of various compositions, which are less brittle.
The fabrication of dental elements in practice is a complex and time consuming affair. The products involved are fabricated on an individual basis since the exact form of the element is different for every tooth or molar in every individual. Conventional techniques that have been used often utilize a mold. Since this mold can typically be used only once, it will be clear that these techniques are very costly.
In the past, techniques have been proposed which supposedly enable simplification of the fabricating process of dental elements. Thus, Abe et al., in Int. J. Japan Soc. Prec. Eng., vol. 30, no. 3, 1996, pp. 278–279, have proposed to carry out a selective laser sintering (SLS) with titanium. This technique, however, often gives rise to shrinkage. Also, microcracks may be formed, which renders the technique unsuitable for the fabrication of functional dental elements. In European patent application 0 311 214 it has been proposed to make a crown by milling. Milling does not provide the possibility of making colored elements. Moreover, the choice of suitable materials that can be processed by milling is limited. As noted, ceramic materials form an ideal group of materials for fabricating dental elements, because they are hard, highly wear-resistant and inert under many conditions.
U.S. Pat. No. 5,690,490 describes a method for fabricating a concept model for a dental element by so-called pinhead molding. The method concerns the use of a kind of matrix printing technique, whereby material is sprayed on. The printer is controlled with a CAD/CAM program. The data which this program utilizes have been obtained from a laser scan of the tooth or the molar to be replaced.
In U.S. Pat. No. 5,823,778, a method is described for the fabrication of a dental element whereby an impression of the teeth of a patient is obtained, which is subsequently used as a mold to make a copy of a dental element. This element is broken down in layers and each layer is scanned to obtain a three-dimensional computer model of the dental element.